Electrical sensor unit for a safety belt retractor

ABSTRACT

The electrical sensor unit for mounting on a conventional safety belt retractor to provide an electrical signal to a &#39;&#39;&#39;&#39;Fasten Safety Belts&#39;&#39;&#39;&#39; light and to a &#39;&#39;&#39;&#39;Safety Belts Fastened&#39;&#39;&#39;&#39; light of a vehicle warning system includes a housing for location on the retractor over the nut on the axle of the belt reel; a hub adapter rotatably mounted in the housing coaxially of the belt reel, with a cavity on the inner end thereof mating with the reel axle nut, and with a gear on the outer end thereof; a ring gear cam rotatably mounted in the housing for rotation about an axis parallel to and spaced from the reel axis to mesh with the hub gear, said ring gear cam having a curved ridge adjacent part of its circumference; an actuator slidably mounted in the housing with the lower end thereof engageable by the surface of the cam ridge to be slid thereby into a raised position; and normally open and normally closed contacts mounted in the housing, electrically connected to the lights, and engageable by the upper end of the actuator to be moved thereby to the other positions to signal, in response to the extension and retraction of the belt, whether or not the safety belt is buckled.

United States Patent 1191 Morales ELECTRICAL SENSOR UNIT FOR A SAFETYBELT RETRACTOR Gerald A. Morales, Simi, Calif.

[73] Assignee: American Safety Equipment Corporation, Encino, Calif.

[22] Filed: June 30, 1971 [21] Appl. No.: 158,285

[75] Inventor:

[ 1 Oct. 23, 1973 [57 ABSTRACT The electrical sensor unit for mountingon a conventional safety belt retractor to provide an electrical signalto a Fasten Safety Belts light and to a Safety Belts Fastened light of avehicle warning system includes a housing for location on the retractorover the nut on the axle of the belt reel; a hub adapter rotatablymounted in the housing cofiiallfi fthe beTtYe l, with a cavity on theinner end thereof mating with the reel axle nut, and with a gear on theouter end thereof; a ring gear cam rotatably mounted in the housing forrotation about an axis parallel to and spaced from the reel axis to meshwith the hub gear, said ring gear cam having a curved ridge adjacentpart of its circumference; an actuator slidably mounted in the housingwith the lower end thereof engageable by the surface of the cam ridge tobe slid thereby into a raised position; and normally open and normallyclosed contacts mounted in the housing, electrically connected to thelights, and engageable by the upper end of the actuator to be movedthereby to the other positions to signal, in response to the extensionand retraction of the belt, whether or not the safety belt is buckled.

23 Claims, 8 Drawing Figures 1 ELECTRICAL SENSOR UNIT FOR A SAFETY BELTRETRACTOR BACKGROUND OF THE INVENTION This invention relates to safetybelt retractors and more particularly to a sensor unit for such aretractor which may be electrically connected to a vehicle warningsystem.

The law requires that safety belts be installed in all new cars andtrucks to protect the occupants of the vehicles against injury in theevent of an accident. However, these safety belts provide no protectionunless the occupants wear them, and unfortunately many times theoccupants neglect to buckle up.

In order to remind the occupants of a vehicle to fasten their seat belt,warning systems have been devised which flash lights, operate buzzers,or even cut out the ignition circuit of the vehicle until the seat beltsare fastened. Such systems require some means of sensing when the beltsare being used and when the belts are not being used. Prior art sensormeans have included the provision of wires through the belt halves whichare connected by buckling the belt halves together (see Hood, U.S. Pat.No. 3,133,277), the provision of belt tension actuated switches whichare opened when the halves are buckled together (see Erikson, U.S. Pat.No. 3,226,674) and the provision of specially constructed retractormechanism which close switches upon withdrawal of the belt (see Lewis etal., U.S. Pat. No. 3,371,736). The most practical of the prior artsensor means are the retractor related ones, but their major drawbackhas been that they required special adaptation of the retractor itself.The Lewis patent for example, shows a safety belt system including sucha specially constructed retractor with an axially extended, threadedbelt reel end along which a switch actuating, threaded follower moves inresponse to extension of the belt to close a switch-in the ignitioncircuit to per mit the engine to be started. Besides requiring aspecially designed retractor, the sensor means of the Lewis patent makesthe retractor too long for installation in many vehicles.

Safety belt retractors have reached a level of design where it would bedesirable to adapt the sensor means to existing retractor with thesensor means so adapted being very compact.

BRIEF DESCRIPTION OF THE INVENTION Therefore, it is the primary objectof this invention to provide an electrical sensor unit which is adaptedto be mounted on an existing safety belt retractor and which connects toa warning system to indicate whether or not the belt is being used.

Other and additional objects of this invention are to provide such anelectrical sensor unit which is compact when mounted to the retractor,which requires a minimum of design changes in the retractor, which ispositively and correspondingly driven by the extension and retraction ofthe belt, which is easily oriented with the position of the belt in theretractor, which will provide one or more electrical signals to thewarning system, which energizes one part of the warning system beforeanother part thereof is deenergized and which is economical tomanufacture, easy to install and dependable in operation.

Generally stated the electrical sensor unit for a safety belt retractorto provide an electrical signal indicating the position of the beltaccording to the present invention includes an operating meansoperatively associated with the belt reel of the retractor to berotatively driven thereby in response to extension and retraction of thebelt, said operating means having a camming surface rotating about anaxis spaced from the axis of the belt reel; and switch means mounted tothe frame of the retractor for being engaged by the camming surface ofthe operating means in certain rotative positions thereof and beingspaced from the camming surface thereof in other rotative positionsthereof to provide the electrical signal. The switch means may includenormally open contacts, normally closed contacts or both as well asactuator means for engagement by the camming surface upon extension ofthe belt to move the contacts to the other position. The operating meansmay include a driver member and a driven member engaging the drivermember and carrying the camming surface. The parts may all be locatedand held in a housing which in turn is easily mounted to an alreadyassembled retractor by novel mounting means. The retractor with thesensor unit may be mounted in a vehicle having a dual light warningsystem and the sensor unit may have a make before break switch means forthe dual light warning system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of thesensor unit, according to this invention, mounted on a conventional seatbelt retractor;

FIG. 2 is an enlarged, exploded perspective view of the sensor unit ofFIG. 1;

FIG. 3 is an enlarged elevational view of the end of the sensor unit ofFIG. 1 facing the retractor;

FIG. 4 is a cross-sectional view of the unit of FIG. 3 taken thereinalong the plane IV-IV;

FIG. 5 is an elevational view, partially in section, of the unit of FIG.4 taken therein along the plane V-V showing the camming surface thereofin a position corresponding to the retracted position of the belt andshowing the electrical contacts of the unit in their normal positions;

FIG. 6 is a view similar to FIG. 5 but showing the camming surfacethereof rotated to an intermediate position with the normally opencontacts moved to the closed position while the normally closed contactsremain in the closed position;

FIG. 7 is a view similar to FIG. 5 and 6 but showing the camming surfacethereof rotated to a position corresponding to the extended position ofthe belt and showing each of the contacts of the unit moved to theirother positions;

FIG. 8 is a schematic wiring diagram of a portion of a vehicleelectrical system which comprises a. vehicle warning system, with whichthe sensor unit, according to this invention, may be used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawings and particularly to FIG. 1, the electrical sensor unitaccording to this invention, is generally denoted by the number 10. Theelectrical sensor unit 10 is shown mounted to an illustrativeconventional safety belt retractor 11 such as in required in every newlymanufactured automobile or truck for use in the United States. Theretractor 11 includes a frame 12 with apertured sidewalls l3 and a web14 with a hole therein through which a conventional bolt is passed inmounting the retractor 11 to the vehicle. A belt reel 15 with the safetybelt strap wound therearound is located between the sidewalls l3 and hasan axle 16 extending through the apertures on the sidewalls 13 torotatably mount the reel 15 therebetween. Conventional hexagonal nuts 17are turned onto the axle ends to maintain the axle 16 on the sidewalls13. The retractor 11 also typically has a biasing means 18 for biasingthe safety belt to the retracted position, i.e., wound upon the reel 15,and has locking means 19 for locking the belt after the belt is fastenedaround the occupants of the vehicle. There are, of course, a great manydesigns of safety belt retractors and the sensor unit is adaptable foruse with most of these designs. The retractor 11 shown is meant to beillustrative of all of these retractors and is not itself part of thisinvention. Generally, the electrical sensor unit 10, according to thisinvention, for providing an electrical signal indicating the position ofa safety belt, includes a housing 20 thereover and adapted for mountingto the frame 11; mounting means 30 mounting the housing 20 to theretractor 11; operating means 40 such as a driver means 41 and a drivenmeans 50, rotatably mounted in the housing 20 and having a cammingsurface 55 for rotation about an axis spaced from the reel axis; switchmeans 60 including either normally open contacts 61 or normally closedcontacts 70 or both and an actuator means 80 for being engaged by thecamming surface 55 to operate the switch means 60 to provide theelectrical signal. The retractor 11, with the sensor unit 10, accordingto this invention, having connector means 90, may be mounted to avehicle having warning system 100 with the connector means 90 connectingthe sensor unit 10 to the warning system 100. Holding means 110 may beprovided in the assembly of the unit 10 for holding the operating means40 in a fixed position until the housing 20 is installed on theretractor 11 to obtain correspondence in the positions'of the partsthereof.

Referring now primarily to FIG. 2, the sensor unit 10 includesa'supporting structure for mounting the parts to the retractor frame 12which is, illustratively, a housing 20. The housing 20 has a transversemiddle wall 21 from which a cylindrical wall 22 extends towards theretractor 11 to define a retractor facing cavity 23 centered on the reelaxis, and from which an opposite cylindrical wall 24 extends away fromthe retractor 11 to define an oppositely facing cavity 25 about an axisparallel to but spaced from the reel axis. The housing 20 has anaperture 26 through the middle wall 21 along the reelaxis to provide apassage between the cavities 23 and 25 for a purpose which will appearlater. A circumferential rib 27 (see FIG. 4) on an extension 28 of thecylindrical wall.24 and three equally spaced, in-

wardly facing shoulders 29 in the cylindrical wall 22,

are provided for a purpose which will. appear later.

The supporting structure of the sensor unit 10 also end wall 32 alongthe reel axis for a purpose which will appear later. The cylindricalwall 33 has apertured tabs 37 formed therein for receiving fasteners 38atherethrough which will extend into mating features 38b in the sidewall13 of the frame 12 for mounting the cap 31 over the housing 20 to theretractor 11. A locating pin 39 is provided for initially locating thecap on the sidewall 13 of the retractor 11 while the fasteners 38 arebeing mated.

The operating means 40 of the sensor unit 10 are operatively associatedwith the belt reel 15 to be rotatively driven thereby in response toextension and retraction of the belt to operate the switch means 60. Theoperating means 40, as best seen in FIG. 2, includes both a driver means41 rotatively driven by the belt reel 15 and a driven means 50 drivinglyengaged by the driver means 41. The driver means 41 of the illustrativeembodiment is a hub adapter 42 which has a cylinder 43 at the retractorend thereof. The cylinder 43, as best seen in FIG. 3, has a femalecavity 44 which is provided with flats for mating with the flats on thenut 17 on the axle 16 to spline the two together. Returning to FIG. 2,the circumference of the cylinder 43 is provided with a bearing ridge 45which rides on inner surface 46 in the cylindrical wall 22 to centrallylocate the cylinder 43 in the retractor facing cavity 23 for rotationtherein.

. A gear 47 extends from the end of the cylinder 43 and is coaxialtherewith. The gear 47 extends through the aperture 26 in the middlewall 21 of the housing 20 to be located in the oppositely facing cavity25. Apin 48 extends coaxially from the gear 47 into the closed bore 36,as best seen in FIG. 4, to rotatably mount the opposite end of the hubadapter 42 to the cap 31'.

A driven means 50 of the illustrative embodiment is a ring gear cam 51with internal teeth for meshing with the teeth of the gear 47. A ridge52 extends about the.

circumference of the ring gear cam 51 and mates with the inner surface53 in the cylindrical wall 24 of the housing 20 to locate and rotatablymount the ring gear cam 51 in the oppositely facing cavity 25 forrotation about an axis spaced'from the axis of the reel 15. The ringgear 51 has a curved ridge 54 in a face thereof which provides a cammingsurface 55 for operating the switch means 60. The camming surface 55includes a ramp portion 56 on either end thereof and a curved portion 57between the ramp portions 56 thereof. The

' driven means 50 is for operating the switch means 60 includes mountingmeans 30 for mounting the housing 20, and the parts mounted thereto, tothe retractor 11, which in the illustrated retractor will be readilycompletely assembled. The mounting means 30 shown includes a cap 31having an end wall 32 and a circumferentially grooved cylindrical wall33, which together define a retractor facing cavity 34 sized to receivethe housing 20 therein. A cutout 35 is provided in the cylindrical wall33 where needed. A raised boss having a closed bore 36 (as seen in FIG.4) is provided 'in the uponrotation thereof by the driver means 41.

The'switch means 60 of the sensor unit 10 is actuated by the operatedmeans 40 when the latter is in certain relatively rotated positionsthereof to provide the electrical signal to the warning system 100. Theswitch means 60 is illustratively shown as having both normally opencontacts 61 and normally closed contacts 70 but because of theversatility of the switchmeans 60 of this invention they could beprovided with either contacts 61 or 70 without any modifications to thesensor unit 10 itself.

As best seen in FIG. 2, the normally open contacts 61 include a returnbent leaf spring 62 with a mounting flange 63 having holes 64. Thenormally open contacts 61 also include a seat 65 with a mounting flange66 having holes 67. The middle wall 21 of the housing 20 has protrusions68 on which the flanges 63 and 66 are located to receive rivets 69therethrough to mount the leaf spring 62 and seat 65 to the housing 20with the relationship as shown in FIG. 5. In FIG. 5, the end of the leafspring 62 is spaced from the seat 65 to provide the normally opencontacts 61.

The normally closed contacts 70 are quite similarly constructed to theconstruction of the normally open contacts 60 and include a return bentleaf spring 71 with a mounting flange 72 with holes 73. The seat 74 hasa mounting flange 75 with holes 76. Again the middle wall 21 of thehousing 20 has protrusions 77 on which the flanges 72 and 75 are locatedto receive rivets 78 therethrough. In FIG. 5, the end of the leaf spring71 engages the seat 75 to provide the normally closed contacts 70. Boththe normally open and normally closed contacts 60 and 70 are moved fromtheir normal position to their other position by contact actuator meansand means mounting the contact actuator means 80.

The contact actuator means and means mounting the contact actuator means80 are part of the switch means 60 and are for moving the contacts 61and 70 from their normal position to their other position. As best seenin FIG. 2, the means 80 illustratively includes a spaced pair ofvertical walls 81 extending from the middle wall 21 of the housing 20.The vertical walls 81 have notches 82 in the outer surface thereof. Anactuator 82 is elongated and has tabs 84 which are located in thenotches 82 to limit the vertical movement of the actuator 83 between alowered position and raised position. The actuator 83 has an upper end85 with an inner or normally closed contact portion 86 and an outer ornormally open contact portion 87 with a wall 88 therebetween. Theactuator 83 has a lower end 89, as seen in FIG. 5, which is spaced fromthe camming surface 55 of the operating means 40 in certain rotativepositions thereof to permit the contacts 61 and 71 to remain in theirnormal positions; which, as seen in FIG. 6, is engaged by the rampportion 56 of the camming surface 55 in certain rotative positionthereof; first to move the normally open contact 61 to the closedposition and then to move the normally closed contact 70 to the openposition thereof while holding the normally open contact 61 in theclosed position; and finally, which as seen in FIG. 7, is engaged by thecurved portion 57 of the camming surface 55 in certain rotativepositions thereof to hold the contacts 61 and 70 in the other positions.This movement provides the electrical signals carried by connectingmeans 90.

The connecting means 90 of the sensor unit are for electricallyconnecting the unit 10 to a warning system 100. As best seen in FIGS. 2and 3 the electrical connecting means 90 include protrusions 91 from themiddle wall 21 of the housing which extend into the retractor facingcavity 23 to receive thereon wire terminals 92 having holes 93. Therivets 69 and 78 also extend through the holes 93 to electricallyconnect the terminals 92 to respective normally open and normally closedcontacts 61 and 70. I Each terminal 92 is mounted on one end of wire 94,the other end of which is mounted in a socket 95 which is easilyconnected to the warning system 100.

The warning system 100 is diagrammatically shown in FIG. 8 and includesa battery or other source of electrical energy 101 which will typicallybe a vehicle battery. One terminal of the battery 101 will be connectedto the sensor unit 10 and the other terminal will be connected to a pairof lights 102 and 103 by wires 104. The light or other signaling device102 in some manner indicates fasten safety belts and the other light orother signaling device 103 indicates safety belts fastened. The lights102 and 103 are connected by wires 104 to the normally closed contactsand the normally open contacts 61 respectfully so that light 102 signalsFasten Safety Belts until the safety belts are fastened whereupon thesensor unit 10 causes the light 103 to signal Safety Belts Fastened.

The sensor unit 10 of the illustrated embodiment, being a completesubassembly which is mounted to the retractor 11 after both areassembled, needs holding means for holding the operating means 40 in apre determined position for mounting to the already assembled retractor11. Illustratively, the holding means 110 includes a hold 111 in thecylindrical wall 24 of the housing 20 and walls 112 in the cap 31 whichdefine a head space 113 as best seen in FIG. 5. The ring gear cam 51 isprovided with a tree 114 which has opposed spring arms 115 extendingoutwardly from a trunk 116 with a break-off notch 117 at the juncture ofthe trunk with the ring gear 51. When the ring gear cam 51 is initiallypositioned in the housing 20, the tree 1 14 extends into the head space113 through the hole 111 to prevent rotation of the ring gear cam 51 inturn holding the positions of the hub adapter 42 and the switch means60.

It is contemplated that the illustrative sensor unit 10 will beassembled as a complete subassembled retractor 11, though by simplechanges in the design of the sensor unit 10, without departing from thescope of this invention, the sensor unit 10 could be assembled with theassembly of the retractor 11. To assemble the sensor unit, the terminals92 attached to the wires 94 from the socket 95; the leaf springs 62 and71; and the seats 65 and 74 are placed on the protrusions 91, 68, and 77of the middle wall 21 of the housing 20 with the rivets 69 and 78securing these parts thereto. Next the ring gear cam 51 is inserted intothe oppositely facing cavity 23 of the housing 20 with the tree 114thereon extending through hole 111 to properly initially locate thecamming surface 55. The actuator 83 is inserted between the spaced walls81 with the tabs 84 located in the notches 82 of the walls 81. Next, thehousing 20, with the parts mounted thereon, is inserted into theretractor facing cavity 34 of the cap 31 until the rib 27 snaps into thegroove in the wall 33 to retain the parts in the space between the cap31 and the housing 20. The hub adapter 42 is now inserted into theretractor facing cavity with the gear 47 thereof extending through theaperture 26 to mesh with the ring gear cam 51, and with the pin 48extending into the bore 36 in the cap 31. While being inserted, thecircumferential ridge 45 snaps behind the shoulders 29 to ride on theinner surface 46. The subassembly of the sensor unit 10 is now complete,ready to be mounted to the retractor 11. I

To mount the sensor unit 10 to the retractor 11, the sensor unit ispositioned adjacent the sidewall 13 to enable the female cavity 44 ofthe hub adapter 42 to be telescoped over the nut 16 in splinedrelationship thereto to be driven thereby. When the sensor unit 10 isflush against the sidewalls 13, the locating pin 39 will properly locatethe unit 10 on the retractor 11 while the fastener 38a is insertedthrough the apertured tabs 37 and into the mating fasteners 38b of thesidewall 13 to secure the sensor unit 10 to the retractor 11. Theretractor 11 is now ready to be mounted in a vehicle with the sensorunit 10 thereof electrically connected via socket 95 to the vehiclewarning system 100.

The operation of the sensor unit 10 is best illustrated by referringsuccessively to FIGS. 5, 6 and 7. In FIG. 5, the sensor unit 10 is shownas initially assembled with the camming surface 55 of the ring gear cam51 in the belt retracted position; with the actuator 83 in the loweredposition with the lower end 89 against the housing and with the normallyclosed contact 70 and the normally open contact 61 in their normalpositions. The normally closed contacts 70 electrically connect theFasten Seat Belts light 102 across the battery 101 to remind theoccupants of the vehicle to buckle up."

As the occupant pulls the belt from the retractor 11 to "buckle up,theme] 15 rotates, rotating the axle l6 and nut 17 to drive the hubadapter 42. The gear 47 of the hub adapter 42 drives the ring gear cam51 to rotate it from the position shown in FIG. 5 to the position shownin FIG. 6. As the ring gear 51 leaves the position shown in FIG. 5, thetree 1 14 is separated from the ring gear 51 at the notch 117 whereuponthe spring arms 115 raise the trunk 116out of the cavity and into thehead space 113 where the tree 114 remains out of the way. As the ringgear cam 51 approaches the position shown in FIG. 6, the ramp portion 56of the camming surface 55 engages the lower end 89 of the actuator 83and raises it to the position of FIG. 6. In the meantime, the normallyopen contact portion 87 of the upper end 85 engages the leaf spring 62to raise it against the seat 65 to close the normally open contact 61and thereby electrically connect the Safety Belts Fastened light 103across the battery 101 to show that the safety belts are fastened.Continued extension of the belt to the actual fastening position,rotates the ring gear cam 51 past the position shown in FIG. 6 and intothe position of FIG. 7. As the ring gear cam 51 passes the position ofFIG. 6, the ramp surface 56 raises the lower end 89 of theactuator 83onto the curved portion 57. The upper end 85 of the actuator 83 alsoraises, whereupon the normally closed contact portion 86 engages theleaf spring 71 to raise it away from the seat 74 and disconnect theFasten Safety Belt light 102 from across the battery 101, leaving onlythe Safety Belts Fastened light 103 on. As long as the safety belts arefastened, the light 103 will remain on.

When the safety belt is released, the biasing means 18 rotates the reel15 oppositely to rotate the ring gear cam 51 from the position of FIG.7, through the position of FIG. 6 to the position of FIG. 5. Theactuator 83 is moved from the raised position to the lowered position bythe spring action of the leaf springs 62 and 71 acting against the upperend 85 while the lower end 89 moves along the curved portion 57 and downthe ramp portion 56 and away from the camming surface 55. The leafspring 71 returns to the seat 74 to energize the Fasten Safety Beltslight 102 before the leaf spring 62 leaves the seat 65 to disconnect theSafety Belts Fastened light 103 from across the battery 101.

It should be noted that the switch means 60 of the sensor unit 10 ofthis invention always provides a "make before break switch action.Another advantage of the sensor unit 10 of this invention, is that onlyone of the contacts 61 and 70 may be used if the partic ular vehiclewarning system 100, so requires, and it can be either, the normally opencontacts 61 or the normally closed contacts 70 depending upon therequirements of the particular warning system 100. If so desired, theextra contacts could be omitted from the sensor unit 10 together withtheir related parts, but it will probably be more economical for suchuses to provide the sensor unit with both contacts 61 and 70 and thenonly use the require set.

Thus, the sensor unit 10 according to this invention is adapted to mountto an existing safety belt retractor and is adapted for connection to avehicle warning system to remind the occupants to use their safety beltsas well as indicating that the seat belts are being used.

I claim:

1. An electrical sensor unit for a conventional safety belt retractor toprovide an electrical signal indicating the position of the belt, saidretractor having a frame and a belt mounting reel rotatably mountedthereto about an axis, said sensor unit comprising:

switch means associated with an electrical signal producing means;

camming means associated with said switch means and means for mountingsaid camming means for rotation about a fixed axis for actuating saidswitch means when said camming means is in certain rotative positionsthereof; and

gear drive means including a drive gear associated with the belt reeland a driven gear associated with the camming means for rotatingsaidcamming means on its mounting means in response to rotation of saidreel upon extension and retraction of the belt. I

2. An electrical sensor unit for a conventional safety belt retractor toprovide an electrical signal indicating the position of the belt, saidretractor having a frame and a belt mounting reel rotatably mountedthereto about an axis, said sensor unit comprising:

switch means associated with an electrical signal producing means;camming means associated with said switch means for actuating saidswitch means when said camming means is in certain rotative positionsthereofj and operating means associated with the belt reel for rotatingsaid camming means in response to rotation of said reel upon extensionand retraction of the belt, wherein the switch means includes: pair ofnormally open contacts and a pair of normally closed contacts formovement between open and closed positions, and contact actuator meansand means for movably mounting the actuator means for engagement by thecamming surface upon extension of the belt to move the contacts fromtheir normally open and normally closed positions to the closed andopened positions, respectively, retraction of the belt returning thecamming means to return the contacts via said contact actuator means totheir normal positions. i 3. The invention as in claim 2 whereintheretra'ctor frame is mounted to a vehicle having warning system thelatter relative to said pair of normally open contacts 7 and said pairof normally closed contacts so that one of said pair of contacts isengaged by said actuator means prior to the other upon movement of saidactuator means whereby upon extension of the belt, one of said pair ofcontacts is actuated prior to the other.

5. An electrical sensor unit for a conventional safety belt retractor toprovide an electrical signal indicating the position of the belt, saidretractor having a frame and a belt mounting reel rotatably mountedthereto about an axis, said sensor unit comprising:

switch means associated with an electrical signal producing means;camming means associated with said switch means for actuating saidswitch means when said camming means is in certain rotative positionsthereof; and

operating means associated with the belt reel for rotating said cammingmeans in response to rotation of said reel upon extension and retractionof the belt, wherein the operating means includes a drive meansrotatively driven by the belt reel and includes a driven means, saiddriven means drivingly engaging the driver means and having thereon thecamming means whereby rotation of the belt reel rotates the cammingmeans between rotative positions to operate the switch means, whereinthe driver means is a gear, and wherein the driven means is a gearmeshing with the driver means gear.

6. The invention as in claim 1 wherein the camming means includes a rampportion for initially engaging the switch means and for moving theswitch means upon engagement therewith to an actuated position, and acurved portion joined to-the ramp portion for maintaining the switchingmeans said position.

7. The invention as in claim 6 wherein the switch means includescontacts movable between a normal position and an actuated position andactuating means for moving the contacts, said actuating means having aportion thereof located for engagement by the camming means, saidportion being initially engaged by the ramp portion to be moved therebyto move the contacts from the normal position to the actuated positionand then engaged by the curved surface to maintain the contacts in theactuated position.

8. The invention as in claim 1 wherein said sensor unit is provided withsupporting structure mounted to the retractor frame which includes meansfor mounting the operating means and switch means to said retractorframe.

9. The invention as in claim 8 wherein the belt reel has an axleextending through one sidewall of the frame, wherein the supportingstructure includes a housing and means are provided for mounting thehousing on the sidewall over a portion of said axle ex- .tending throughsaid one sidewall of the frame.

10. The invention as in claim 9 wherein the operating means includes adriver means associated with the axle to be rotatively driventhereby andincludes a driven means rotatively mounted in the housing for beingdrivenly engaged by the driver means and wherein the camming means ismounted on said driven means whereby rotation of the belt reel rotatesthe camming means between rotated positions to operate the switch means.

11. The invention as in claim 9 wherein the operating means includes adriver means, and wherein the reel axle and the driver means have matingmale and female ends to lock the two together for correspondingrotation.

12. The invention as in claim 11 wherein the reel axle has a nut on theend thereof, and wherein the driver means has a mating cavity in the endthereof.

13. The invention as in claim 9 wherein the operating means and theswitch means are movably mounted to the housing, said operating meansengaging the axle upon the mounting of the housing to the sidewall bythe mounting means.

14. An electrical sensor unit for installation on an already assembledconventional safety belt retractor to provide an electrical signalindicating the position of the safety belt, said retractor having aframe and a belt mounting reel with an axle extending through at leastone sidewall of the frame, said sensor unit comprising:

a hollow housing suitably shaped for location to the one sidewall overthe axle,

an operating means movably mounted in the housing for engaging the axleto be correspondingly driven by the axle upon rotation of the reel dueto extension and retraction of the belt, switch means mounted in thehousing for being operated by the operating means upon movement thereofto provide the electrical signal, and

mounting means for mounting the housing, with the operating means andthe switch means already mounted therein, on the sidewalls over the axlewith the operating means engaging the axle to be driven thereby. 15. Theinvention as in claim 14 wherein: a first spline member is fixedlyprovided on said reel axle exteriorly of said frame one sidewall andsaid operating means for engaging the axle includes a second splinemember, said first and second spline members being interfitted to eachother upon mounting of the housing to said one sidewall for driving saidoperating means by said reel axle upon rotation of said reel.

16. The invention as in claim 14 wherein the reel axle has a nutadjacent the sidewall and wherein the operating means includes a drivermeans having a mating cavity, said nut being received in said cavitywhen said housing is mounted to the retractor to be driven thereby.

17. The invention as in claim 14 wherein the switch means includes anactuating means located spaced from the axis of the reel and wherein theoperating means includes a driver means rotatably mounted in the housingfor engaging the axle and includes driven means movably mounted in thehousing radially of and in association with the driver means, to movethe actuating means and thereby operate the switch means.

18. The invention as in claim 17 wherein the driven means includes a hubadapter rotatably mounted in the housing coaxial with the reel, when thehousing is mounted to the frame, with one end engaging the reel axle andthe other end provided with a gear; wherein the driven means is antoothed gear cam rotatably mounted in the housing for rotationalmovement about an axis parallel to and spaced from the reel axis to meshwith the hub adaptor gear and to be located adjacent the end of theswitch means actuator, said gear cam having a curved ridge with acamming surface for engaging the end of the actuator in certain rotativepositions of the gear cam to move the actuator, and for 1 1 being spacedfrom the end of the actuator in certain other rotative positions.

19. The invention as in claim 14 wherein the switch means includes apair of normally closed contacts mounted in the housing for movementbetween closed and open positions, and

a contact actuator means and means for movably mounting the actuatormeans in the housing for engagement by the camming surface uponextension of the belt to separate the normally closed contacts,retraction of the belt returning the camming means to return thecontacts to the closed position.

20. The invention as in claim 14 wherein the switch means includes g apair of normally open contacts mounted in the housing for movementbetween open and closed positions, and

a contact actuator means and means for movably mounting the actuatormeans in the housing for engagement by the camming surface uponextension of the belt to move the normally open contacts to the closedposition, retraction of the belt returning the camming surface to returnthe contacts to the closed position. g 21. The invention as in claim 14wherein the switch means includes 4 v a pair of normally open contactsand a pair of normally closed contacts, mounted in the housing for 12movement between open andclosed positions, and a contact actuator meansand means for movably mounting the actuator means in the housing forengagement by the camming surface upon extension of the belt to move thecontacts from the normal position to the other position, retraction ofthe belt returning the camming means to return the contacts to thenormal position.

22. The invention as in claim 20 wherein the retractor frame is mountedto a vehicle having warning system with two indicators, one indicatorsignaling that the safety belt is not fastened and the other indicatorsignaling that the safety belt is fastened, said one indicator beingconnected to the normally closed contacts and said other indicator beingconnected to the normally open contacts whereby when the safety belt isretracted, the one indicator signals and when the safety belt isextended the other indicator signals.

23. The invention as in claim 14 additionally comprising holding meansfor holding the operating means in a predetermined position before thehousing is mounted to the retractor by the mounting means, said holdingmeans being for obtaining correspondence between the belt and theoperating means, and for releasing the operating means upon the initialextension of the belt after the mounting of the housing'on the retrac-'tor. v

1. An electrical sensor unit for a conventional safety belt retractor toprovide an electrical signal indicating the position of the belt, saidretractor having a frame and a belt mounting reel rotatably mountedthereto about an axis, said sensor unit comprising: switch meansassociated with an electrical signal producing means; camming meansassociated with said switch means and means for mounting said cammingmeans for rotation about a fixed axis for actuating said switch meanswhen said camming means is in certain rotative positions thereof; andgear drive means including a drive gear associated with the belt reeland a driven gear associated with the camming means for rotating saidcamming means on its mounting means in response to rotation of said reelupon extension and retraction of the belt.
 2. An electrical sensor unitfor a conventional safety belt retractor to provide an electrical signalindicating the position of the belt, said retractor having a frame and abelt mounting reel rotatably mounted thereto about an axis, said sensorunit comprising: switch means associated with an electrical signalproducing means; camming means associated with said switch means foractuating said switch means when said camming means is in certainrotative positions thereof; and operating means associated with the beltreel for rotating said camming means in response to rotation of saidreel upon extension and retraction of the belt, wherein the switch meansincludes: a pair of normally open contacts and a pair of normally closedcontacts for movement between open and closed positions, and a contactactuator means and means for movably mounting the actuator means forengagement by the camming surface upon extension of the belt to move thecontacts from their normally open and normally closed positions to theclosed and opened positions, respectively, retraction of the beltreturning the camming means to return the contacts via said contactactuator means to their normal positions.
 3. The invention as in claim 2wherein the retractor frame is mounted to a vehicle having warningsystem with two indicators, one indicator signaling that the safety beltis not fastened and the other indicator signaling that the safety beltis fastened, said one indicator being connected to the normally closedcontacts and said other indicator being connected to the normally opencontacts whereby when the safety belt is retracted, the one indicatorsignals and when the safety belt is extended, the other indicatorsignals.
 4. The invention as in claim 2 wherein the means for movablymounting the contact actuator means mounts the latter relative to saidpair of normally open contacts and said pair of normally closed contactsso that one of said pair of contacts is engaged by said actuator meansprior to the other upon movement of said actuator means whereby uponextension of the belt, one of said pair of contacts is actuated prior tothe other.
 5. An electrical sensor unit for a conventional safety beltretractor to provide an electrical signal indicating the position of thebelt, said retractor having a frame and a belt mounting reel rotatablymounted thereto about an axis, said sensor unit comprising: switch meansassociated with an electrical signal producing means; camming meansassociated with said switch means for actuating said switch means whensaid camming means is in certain rotative positions thereof; andoperating means associated with the belt reel for rotating said cammingmeans in response to rotation of said reel upon extension and retractionof the belt, wherein the operating means includes a drive meansrotatively driven by the belt reel and includes a driven means, saiddriven means drivingly engaging the driver means and having thereon thecamming means whereby rotation of the belt reel rotates the cammingmeans between rotative positions to operate the switch means, whereinthe driver means is a gear, and wherein the driven means is a gearmeshing with the driver means gear.
 6. The invention as in claim 1wherein the camming means includes a ramp portion for initially engagingthe switch means and for moving the switch means upon engagementtherewith to an actuated position, and a curved portion joined to theramp portion for maintaining the switching means said position.
 7. Theinvention as in claim 6 wherein the switch means includes contactsmovable between a normal position and an actuated position and actuatingmeans for moving the contacts, said actuating means having a portionthereof located for engagement by the camming means, said portion beinginitially engaged by the ramp portion to be moved thereby to move thecontacts from the normal position to the actuated position and thenengaged by the curved surface to maintain the contacts in the actuatedposition.
 8. The invention as in claim 1 wherein said sensor unit isprovided with supporting structure mounted to the retractor frame whichincludes means for mounting the operating means and switch means to saidretractor frame.
 9. The invention as in claim 8 wherein the belt reelhas an axle extending through one sidewall of the frame, wherein thesupporting structure includes a housing and means are provided formounting the housing on the sidewall over a portion of said axleextending through said one sidewall of the frame.
 10. The invention asin claim 9 wherein the operating means includes a driver meansassociated with the axle to be rotatively driven thereby and includes adriven means rotatively mounted in the housing for being drivenlyengaged by the driver means and wherein the camming means is mounted onsaid driven means whereby rotation of the belt reel rotates the cammingmeans between rotated positions to operate the switch means.
 11. Theinvention as in claim 9 wherein the operating means includes a drivermeans, and wherein the reel axle and the driver means have mating maleand female ends to lock the two together for corresponding rotation. 12.The invention as in claim 11 wherein the reel axle has a nut on the endthereof, and wherein the driver means has a mating cavity in the endthereof.
 13. The invention as in claim 9 wherein the operating means andthe switch means are movably mounted to the housing, said operatingmeans engaging the axle upon the mounting of the housing to the sidewallby the mounting means.
 14. An electrical sensor unit for installation onan already assembled conventional safety belt retractor to provide anelectrical signal indicating the position of the safety belt, saidretractor having a frame and a belt mounting reel with an axle extendingthrough at least one sidewall of the frame, said sensor unit comprising:a hollow housing suitably shaped for location to the one sidewall overthe axle, an operating means movably mounted in the housing for engagingthe axle to be correspondingly driven by the axle upon rotation of thereel due to extension and retraction of the belt, switch means mountedin the housing for being operated by the operating means upon movementthereof to provide the electrical signal, and mounting means formounting the housing, with the operating means and the switch meansalready mounted therein, on the sidewall over the axle with theoperating means engaging the axle to be driven thereby.
 15. Theinvention as in claim 14 wherein: a first spline member is fixedlyprovided on said reel axle exteriorly of said frame one sidewall andsaid operating means for engaging the axle includes a second splinemember, said first and second spline members being interfitted to eachother upon mounting of the housing to said one sidewall for driving saidoperating means by said reel axle upon rotation of said reel.
 16. Theinvention as in claim 14 wherein the reel axle has a nut adjacent thesidewall and wherein the operating means includes a driver means havinga mating cavity, said nut being received in said cavity when saidhousing is mounted to the retractor to be driven thereby.
 17. Theinvention as in claim 14 wherein the switch means includes an actuatingmeans located spaced from the axis of the reel and wherein the operatingmeans includes a driver means rotatably mounted in the housing forengaging the axle and includes driven means movably mounted in thehousing radially of and in association with the driver means, to movethe actuating means and thereby operate the switch means.
 18. Theinvention as in claim 17 wherein the driven means includes a hub adaptorrotatably mounted in the housing coaxial with the reel, when the housingis mounted to the frame, with one end engaging the reel axle and theother end provided with a gear; wherein the driven means is an toothedgear cam rotatably mounted in the housing for rotational movement aboutan axis parallel to and spaced from the reel axis to mesh with the hubadaptor gear and to be located adjacent the end of the switch meansactuator, said gear cam having a curved ridge with a camming surface forengaging the end of the actuator in certain rotative positions of thegear cam to move the actuator, and for being spaced from the end of theactuator in certain other rotative positions.
 19. The invention as inclaim 14 wherein the switch means includes a pair of normally closedcontacts mounted in the housing for movement between closed and openpositions, and a contact actuator means and means for movably mountingthe actuator means in the housing for engagement by the camming surfaceupon extension of the belt to separate the normally closed contacts,retraction of the belt returning the camming means to return thecontacts to the closed position.
 20. The invention as in claim 14wherein the switch means includes a pair of normally open contactsmounted in the housing for movement between open and closed positions,and a contact actuator means and means for movably mounting the actuatormeans in the housing for engagement by the camming surface uponextension of the belt to move the normally open contacts to the closedposition, retraction of the belt returning the camming surface to returnthe contacts to the closed position.
 21. The invention as in claim 14wherein the switch means includes a pair of normally open contacts and apair of normally closed contacts, mounted in the housing for movementbetween open and closed positions, and a contact actuator means andmeans for movably mounting the actuator means in the housing forengagement by the camming surface upon extension of the belt to move thecontacts from the normal position to the other position, retraction ofthe belt returning the camming means to return the contacts to thenormal position.
 22. The invention as in claim 20 wherein the retractorframe is mounted to a vehicle having warning system with two indicators,one indicator signaling that the safety belt is not fastened and theother indicator signaling that the safety belt is fastened, said oneindicator being connected to the normally closed contacts and said otherindicator being connected to the normally open contacts whereby when thesafety belt is retracted, the one indicator signals and when the safetybelt is extended the other indicator signals.
 23. The invention as inclaim 14 additionally comprising holding means for holding the operatingmeans in a predetermined position before the housing is mounted to theretractor by the mounting means, said holding means being for obtainingcorrespondence between the belt and the operating means, and forreleasing the operating means upon the initial extension of the beltafter the mounting of the housing on the retractor.